CN101265073B - Composite silica brick and its preparation method - Google Patents

Abstract

A nanocomposite silica brick and its preparation method, characterized in that: the silica brick raw material and binder include: silica particles and fine powder, waste silica brick particles, nano calcium carbonate, nano iron oxide, nano silicon dioxide, fluorite powder, Lime, sulfurous acid pulp waste liquid. The present invention is based on the conventional production process of silica bricks at present, mixes composite nanometer powder in an optimal ratio, introduces it into the brick making process of silica bricks after efficient dispersion, and prepares nanocomposite silica bricks. The performance of silica bricks is significantly improved after adding nano powder, which is embodied in: 1) the particle size distribution is more reasonable, the packing is tight, and the structure is uniform; 2) the mud has strong plasticity, good forming performance, and improved production efficiency; 3) it can reduce burning. The forming temperature is 20°C, and the effect of energy saving and consumption reduction is obvious; 4) Phospho-quartz crystallization transformation is good, and the residual quartz content is low; 5) The closed pores increase, the open pores decrease, the porosity decreases, and the strength and load softening temperature increase; 6) The appearance of the product is good , The surface of the port is smooth, the combination is good, and the qualified rate of the finished product is improved.

Description

Composite silica brick and its preparation method

technical field

The invention belongs to the technical field of inorganic non-metallic materials (refractory materials), and specifically relates to a composite silica brick and a preparation method thereof. The various nano powders used refer to nano calcium carbonate, nano iron oxide and nano silicon dioxide.

Background technique

Silica brick is a traditional refractory product with _SiO2 as the main component. It is an acidic refractory material. It has high temperature volume stability, good thermal conductivity, excellent resistance to acid slag erosion, and especially a high softening temperature under load (only the same as the refractoriness. 30 ~ 50 ℃ difference) and other characteristics. The main raw material for making silica bricks is silica (quartzite). Our country began to produce general silica bricks in the 1930s, and began to mass produce silica bricks for steelmaking open hearth furnaces and coke ovens in the early 1950s. For half a century, with the elimination of steelmaking open hearth furnaces, the use of silica bricks is currently mainly concentrated in coke ovens, blast furnaces and glass kilns. However, the manufacturing process and technology of silica bricks have not undergone major changes for a long period of time.

Due to the large volume expansion caused by the rapid crystal transformation of silica during heating, the firing of silica bricks is more difficult than other refractory materials. The core technology of making silica bricks is the selection and application of mineralizers, the purpose of which is to control the volume expansion of silica bricks caused by the large stress in the bricks due to the crystal transformation of silica during the firing process, so as to prevent the silica bricks from Cracks when fired. When firing silica bricks, it is required to convert quartz into stable high-temperature mineral phases tridymite and cristobalite as much as possible. In order to promote this transformation, mineralizers are usually added in the process of making silica bricks. Mineralizer is an oxide that can react with _SiO2 to form a liquid phase. Its function is to accelerate the transformation of quartz without significantly reducing the refractoriness of the product, and can inhibit the stress caused by expansion when the brick is fired, preventing the product from loosening or cracking.

The manufacturing process determines the mineral phase composition and product quality of silica bricks. At the same firing temperature, the type, particle size and amount of mineralizer determine the mineral phase composition and relative content. When the mineralizer exists, the transformation process of quartz is: 1β-quartz rapidly transforms into α-quartz at 573°C, and in the range of 1200-1470°C, α-quartz rapidly transforms into metastable cristobalite. At the same time, α-quartz, metastable cristobalite interacts with mineralizers and impurities to form a liquid phase, and invades quartz particles and cracks generated when metastable cristobalite is formed, promoting the continuous dissolution of α-quartz and metastable cristobalite In the formed liquid phase, it becomes a supersaturated melt of silicon and oxygen, and then gradually crystallizes out of the melt in the form of stable tridymite. The conversion speed of this process depends on the physical and chemical properties and quantity of the mineralizer. The action capacity of the mineralizer mainly depends on the properties of the melt formed by the mineralizer and silicon oxygen in the brick adobe at high temperature, as well as its distribution and quantity, namely: the temperature at which the liquid phase begins to form, the viscosity and the wetness of the liquid phase. Wetting capacity, liquid phase structure, quantity, distribution and other factors.

An ideal mineralizer should meet the following conditions:

1) It should be able to interact with _SiO2 to form a liquid phase at a relatively low temperature (generally below 1300°C), and have little effect on the refractoriness of the product;

2) The viscosity of the generated liquid phase is low and has good wettability to the surface of quartz particles;

3) The amount of liquid phase generated does not change much with the increase of temperature;

4) The mineralizer should be dispersed and evenly distributed as much as possible during the brick making process;

5) The mineralizer is not water-soluble, and does not migrate and precipitate when the brick is dried.

At present, most of the mineralizers used in the production of silica bricks are iron oxide and calcium oxide. They not only have the above characteristics, but also can ensure that silica bricks have good high-temperature mechanical properties. However, iron oxide and calcium oxide used in production are added in the form of fine powder and milk of lime respectively. Compared with nano-scale powder, the particle size of the former is not fine enough, and the dispersion in the silica brick is not uniform enough; the latter actually adds It is calcium hydroxide, and its lime milk solution is easy to flocculate and not easy to disperse, so the effect as a mineralizer is poor. The use of nano-scale mineralizers not only greatly improves the uniformity of dispersion, but also improves the microstructure of silica bricks, promotes sintering, reduces the firing temperature, and improves the performance of products.

Contents of the invention

The object of the present invention is to develop a kind of composite silica brick (nano-calcium carbonate, nano-iron oxide, nano-silicon dioxide) and preparation method thereof for the problems existing in the prior art of above-mentioned silica brick production.

The purpose of the present invention is to use the filling effect of nano-silica powder to increase the bulk density of the product; to use the nano-calcium carbonate powder with fine particle size, easy to decompose, and generate highly active calcium oxide after decomposition, and the high dispersion and high efficiency of nano-iron oxide Mineralization and other advantages to improve the shortcomings of the mineralizers currently used in the production of silica bricks, and prepare a nanocomposite silica brick with excellent performance.

The present invention is achieved through the following technical solutions: the raw materials and binders used in the silica brick containing various nanopowders in the present invention include: silica particles and fine powder, waste silica brick particles, nano calcium carbonate, nano iron oxide, nano Silica, fluorite powder, lime, sulfurous acid pulp waste liquid, the weight percent scope of each raw material is as follows:

Silica granules and fine powder 80-90%

Waste silica brick particles 5～15%

Nano calcium carbonate 0.5～2%

Nano iron oxide 0.5～2%

Nano silica 1.0～2%

Lime 0.5～2%

Fluorite powder 0.2～1%

Sulfurous acid pulp waste liquid 0.5～2%

In the whole raw material of the present invention, the mass ratio of aggregate (i.e. silica and waste silica brick particles) to fine powder is (60%-70%)/(40%-30%), and the chemical composition of silica is required to be _SiO2 ≥98.0%.

_The nano _- calcium carbonate used refers to the hydrophilic calcium carbonate powder with _a particle size of less than 100nm. Its purity is required to be ≥90.0%; nano-silica is a powder with a particle size of less than 100nm, and its chemical composition requires its purity to be ≥98.5%.

In the present invention, the CaO content of the lime is required to be ≥ 96.0%, and it is added in the form of water emulsion, and the specific gravity of the lime milk is 1.2-1.3; the purity of the fluorite powder is required to be ≥ 80.0%.

The binder sulfurous acid pulp waste liquid (specific gravity 1.1-1.2) used in the present invention is a temporary binder, which only provides the strength of the green body for the molding of silica bricks, and densifies and generates strength through liquid phase sintering at high temperatures.

The preparation method of the silica brick containing various nanometer powders of the present invention is as follows: first premix the fine powder part other than the nanometer powder, predisperse nanometer calcium carbonate, nanometer iron oxide and nanometer silicon dioxide in water to form a slurry, and mix In the mill, the granules, mixed powder, mixed slurry of three kinds of nano-powders, milk of lime, and sulfurous acid pulp waste liquid are fully mixed and uniform, and then pressed into bricks by machine, and dried until the residual moisture is not more than 1%. Firing in a downdraft kiln, a shuttle kiln or a tunnel kiln, the highest firing temperature is not higher than 1420°C to obtain the nanocomposite silica brick of the present invention.

The present invention has the following advantages:

1. Due to the small particle size of nano-calcium carbonate, it begins to decompose at a relatively low temperature (about 690°C), and it is basically completely decomposed at 800°C. The nano-scale calcium oxide particles generated by decomposition have high specific surface area and reactivity, and are highly uniformly dispersed inside the silica brick. During the firing process of silica bricks, nano-scale calcium oxide reacts with silica to produce high-efficiency mineralization, thereby achieving the purpose of promoting sintering and improving performance.

2. Due to the fine particle size of nano-iron oxide (FeO and Fe ₂ O ₃ ), it can be highly uniformly dispersed inside the silica brick, which can produce high-efficiency mineralization during the firing process, promote sintering, and make the silica brick have a more uniform structure , which can improve the strength and thermal shock resistance of the product.

3. Due to the fine particle size of nano-silica powder, it can fill fine pores, thereby reducing the porosity of the product and increasing the bulk density.

4. The production process of silica bricks containing composite nano-powder (nano-calcium carbonate, nano-iron oxide, nano-silicon dioxide) has not been changed due to the use of nano-powder, no need to increase equipment, and the existing production process of silica bricks is maintained, suitable for large-scale Industrial production.

5. The nano-calcium carbonate, nano-iron oxide, and nano-silicon dioxide used in the present invention do not contain polluting discharges, do not contain radioactivity, and are added in the form of pre-dispersion into a slurry, so the utilization rate is high and there is no dust pollution.

6. The nano-calcium carbonate, nano-iron oxide, and nano-silicon dioxide used in the present invention are easy to source, relatively low in price compared with other oxide nanopowders, and suitable for industrial production.

Detailed ways

The feature of the present invention is that by introducing nano-calcium carbonate, nano-iron oxide and nano-silicon dioxide, the volume expansion of silica bricks caused by crystal transformation during the firing process is suppressed, the conversion of quartz is promoted, and the porosity is reduced. , Increased bulk density, promoted sintering, increased strength, and improved thermal shock resistance. The production process of silica bricks containing composite nano powder is the same as the current production process. The main raw materials (including aggregate and fine powder) are silica and waste silica bricks, and the two are used together.

The following examples illustrate the implementation and characteristics of the present invention, but the present invention is not limited to the following examples. In order to fully illustrate the characteristics of the present invention, the comparative sample of the corresponding actual production technology is provided for each embodiment, and the comparative sample is made mineralizer by adding iron oxide fine powder (≤0.088mm) and milk of lime (introducing calcium oxide) , the content of introducing iron oxide and calcium oxide is equivalent to that of the examples, and the two are compared.

Example 1: The proportioning of each component is (mass percentage) aggregate (wherein silica particles 52%, waste silica brick particles 8%) 60%, silica powder 35%, nano-calcium carbonate powder 2.0%, nano-iron oxide 0.5%, nano silicon dioxide 1.5%, lime 0.5%, fluorite powder 0.5%, sulfurous acid pulp waste liquid 2% (additional).

Comparative example 1: The proportion of each component is (mass percentage) aggregate (silica and waste silica brick particles) 60%, silica powder 36.5%, iron oxide powder 0.5%, lime 2.0%, fluorite powder 0.5%, sulfurous acid pulp Waste liquid 2% (additional).

Embodiment 2: The proportioning of each component is (mass percentage) aggregate (wherein silica particle 55%, waste silica brick particle 10%) 65%, silica powder 28.5%, nano-calcium carbonate powder 1.0%, nano-iron oxide 1.0 %, nano silicon dioxide 2.0%, lime 1.5%, fluorite powder 1.0%, sulfurous acid pulp waste liquid 1.5% (additional).

Comparative example 2: The ratio of each component is (mass percentage) aggregate (silica and waste silica brick particles) 65%, silica powder 31.5%, iron oxide 1.0%, lime 1.5%, fluorite powder 1.0%, sulfurous acid pulp waste Liquid 1.5% (additional).

Embodiment 3: the proportioning of each component is (mass percentage) aggregate (wherein silica particle 55%, waste silica brick particle 15%) 70%, silica powder 24.5%, nano-calcium carbonate powder 0.8%, nano-iron oxide 1.5% %, nano silicon dioxide 1.2%, lime 1.0%, fluorite powder 0.5%, sulfurous acid pulp waste liquid 1.0% (additional).

Comparative example 3: the proportion of each component is (mass percentage) aggregate (silica and waste silica brick particles) 70%, silica powder 26.0%, iron oxide 1.5%, lime 2.0%, fluorite powder 0.5%, sulfurous acid pulp waste Liquid 1.0% (additional).

According to the above ratio, pre-mix the fine powder part other than the nano-powder evenly, pre-disperse the nano-calcium carbonate, nano-iron oxide and nano-silicon dioxide in water to make a slurry, and mix the particles, mixed powder, After the mixed slurry of three kinds of nanometer powder, lime milk, and sulfurous acid pulp waste liquid are fully mixed, they are pressed into bricks with a machine, and the bricks are dried until the residual moisture is not more than 1%. Firing in a tunnel kiln, the highest firing temperature is not higher than 1420°C, that is, the composite nano-silicon-containing brick of the present invention is obtained, and its properties are shown in the attached table.

Schedule:

performance Example 1 Comparative example 1 Example 2 Comparative example 2 Example 3 Comparative example 3 Porosity, % 16.5 19.3 18.3 20.3 19.2 22.1 Bulk density, g/cm³ 2.07 1.98 2.00 1.93 1.96 1.90 Compressive strength, MPa 65.5 56.0 62.8 45.0 61.0 47.0 Residual quartz, % 0.3 1.2 0.5 1.5 0.5 2.0 Firing temperature, ℃ 1420 1440 1420 1440 1420 1440 Qualified rate of finished product, % 96 85 94 84 92 84

Claims (9)

1. composite silicon brick, it is characterized in that: used raw material and wedding agent comprise silica granule and fine powder, useless silica brick particle, nano-calcium carbonate, nano-sized iron oxide, nano silicon, fluorite powder, lime and lignosulfite, and each raw material weight per-cent is as follows:

Silica granule and fine powder 80～90%

Useless silica brick particle 5～15%

Nano-calcium carbonate 0.5～2%

Nano-sized iron oxide 0.5～2%

Nano silicon 1.0～2%

Milk of lime 0.5～2%

Fluorite powder 0.2～1%

Lignosulfite 0.5～2%

The particulate material in the silica brick and the mass ratio of fine powder material are (60%～70%)/(40%～30%).

2. composite silicon brick according to claim 1 is characterized in that: the chemical ingredients of silica requires to be SiO ₂〉=98.0%.

3. composite silicon brick according to claim 1 is characterized in that: nano-calcium carbonate is the wetting ability powder of granularity less than 100nm, and Chemical Composition requires CaCO ₃〉=95.0%.

4. composite silicon brick according to claim 1 is characterized in that: nano-sized iron oxide is FeO and/or Fe ₂O ₃, being the powder of granularity less than 100nm, Chemical Composition requires its purity 〉=90.0%.

5. composite silicon brick according to claim 1 is characterized in that: nano silicon is the powder of granularity less than 100nm, and Chemical Composition requires its purity 〉=98.5%.

6. composite silicon brick according to claim 1 is characterized in that: CaO content requirement 〉=96.0% of lime, add with water and milk shape form, and the proportion of milk of lime is 1.2～1.3.

7. composite silicon brick according to claim 1 is characterized in that: the purity requirement of fluorite powder 〉=80.0%.

8. composite silicon brick according to claim 1 is characterized in that: the proportion of lignosulfite is 1.1～1.2.

9. press the preparation method of the described composite silicon brick of claim 1, it is characterized in that: the fine powder part beyond the first pre-mixing nano powder, with nano-calcium carbonate, nano-sized iron oxide and nano silicon be the pre-dispersed slurry of making in water, in mixing pan with particle, powder mix, the mixture slurry of three kinds of nano powders, after milk of lime and lignosulfite thorough mixing are even, become adobe with machine pressing, after body drying to residual water-content is not more than 1%, at down-draft kiln, burn till in shuttle kiln or the tunnel furnace, maximum sintering temperature is not more than 1420 ℃, promptly makes composite silicon brick of the present invention.